The Greybeards seem to think so ...:"Then it is too late. The lie has already taken root in the hearts of men. So we shall expose to them the falseness in their hearts by tearing out yours, Deceiver! When Lord Miraak appears all shall bear witness. None shall stand to oppose him!"

I don't know what you're talking about:"Your lies fall on deaf ears, Deceiver! We know you are the False Dragonborn! You shall not stand in the way of the true Dragonborn's return. He comes soon, and we shall offer him your heart! When Lord Miraak appears all shall bear witness. None shall stand to oppose him!"

Further encounters will occur in Skyrim and Solstheim from time to time until Miraak is defeated.

After traveling to Solstheim, Cultists will appear inside the Temple of Miraak and around some All-Maker Stones.
After the completion of the main Dragonborn questline, two cultists will spawn outside the Temple of Miraak and respawn after a given time.

An Ascendant Cultist is the strongest form of regular Cultist. They are not as powerful as the boss level Arch Cultist, but are more powerful than the Cultist Adepts. They use lightning spells, including Lightning Storm.

The Master Cultist is the second strongest cultist, and the weakest boss cultists. They attack much like a regular cultist using fire or shock spells. Master cultists use the same spell set as ascendant cultists. They have more health and magicka than other cultists.

An Arch Cultist is the strongest form of Cultist. They are typically bosses and use lightning spells, including Lightning Storm. At times they can be very sloppy and slow and can be taken advantage of at this time.